e nf  SUjniip  Jalanii  atth  limnin' tire  plantations 


NUMBERED  SERIES 


NO.  1 


BULLETIN 


OF 


R.  I.  State  Board  of  Agriculture 


John  J.  Dunn,  Secretary 


THE  ARMY  WORM 


CLIFTON  W.  LOVELAND 
Assistant  Entomolu^^w, , 

V' 


JUNE,  19d#y  ^ 1940 


K®  , t 

V&  "W 


PROVIDENCE: 

E.  L.  FREEMAN  CO.,  STATE  PRINTERS 

1915 


of  lUfflite  JtaLutb  mb  Jlnrotitettr?  {Uattfotuma 


NUMBERED  SERIES 


NO.  1 


BULLETIN 


R.  I.  State  Board  of  Agriculture 

John  J.  Dunn,  Secretary 

THE  ARMY  WORM 


CLIFTON  W.  LOVELAND 
Assistant  Entomologist 


JUNE,  1915 


PROVIDENCE : 

E.  L.  FREEMAN  CO.,  STATE  PRINTERS 

1915 


THE  LIBRARY  OF  THE 

jijrj  8 - 1C49 


i' 


FOREWORD 


This  bulletin  is  one  of  a number  dealing  with  insects  especially 
injurious  to  cultivated  plants,  which  is  being  published  by  the 
entomological  department  of  the  State  Board  of  Agriculture.  These 
bulletins  are  made  as  brief  and  concise  as  possible  and  contain  only 
information  of  value  from  a practical  standpoint.  This  information 
is  based  on  the  latest  data  and  observation  obtainable. 


A.  E.  STENE, 
State  Entomologist. 


THE  ARMY  WORM 


£3a.9 

H©  i 


5 


The  Army  Worm  (. Leucania  unipuncta)  was  present  in  Rhode 
Island  during  the  summer  of  1914,  in  far  greater  numbers  than  for 
many  years  It  became  a veritable  pest  in  many  sections  of  the 
state,  causing  damage  to  the  extent  of  many  thousands  of  dollars 
in  oats,  grass,  millet,  and  corn.  The  insect  was  first  observed  on  the 
grounds  around  the  State  House  on  July  15th  by  Mr.  John  J.  Dunn, 
Secretary  of  the  State  Board  of  Agriculture.  Soon  after  this  date, 
reports  of  its  presence  came  in  hourly  accompanied,  usually,  with 
requests  for  help  to  suppress  it  from  doing  further  damage. 

The  Entomologist  and  the  Assistant  Entomologist  were  kept  very 
busy  visiting  infested  farms  and  showing  the  owners  ways  and  means 
of  controlling  this  insect.  The  worst  infestations  were  in  the  City  of 
Providence,  in  Arlington,  Knightsville,  Lincoln,  Middletown,  and  on 
Block  Island.  In  these  sections  the  Army  Worm  was  present  in 
countless  numbers  and  did  an  enormous  amount  of  damage  in  a few 
days.  Whole  fields  of  millet,  rowen,  and  oats  were  despoiled  before 
the  owners  knew  of  its  presence.  This  was  partly  due  to  the  fact 
that  there  had  been  no  severe  infestation  of  the  Army  Worm  in  a good 
many  years,  so  that  no  special  watch  was  kept  for  it,  and  partly  to 
the  habits  of  the  worm  itself. 

The  Army  Worm  is  always  present  in  grass  lands,  though  generally 
not  in  sufficient  numbers  to  do  conspicuous  damage.  Ordinarily, 
it  acts  in  a manner  similar  to  that  of  its  near  relative  the  cutworm  in 
feeding  at  night  and  in  hiding  under  ground  during  the  day.  Because 
of  this  fact,  it  may  be  readily  overlooked  although  present  in  a field 
in  goodly  numbres.  It  is  only  in  years  of  exceeding  abundance,  such 
as  was  the  case  during  the  summer  of  1914,  that  it  assumes  the  army 
habit  of  marching  from  field  to  field  in  its  search  for  provender. 


4 


In  most  of  the  cases,  the  Army  Worm  had  its  start  in  old  grass  land 
which  had  not  been  turned  over  in  several  years.  As  small,  almost 
black  larvae  (Fig.  5a)  they  fed  on  the  lower  leaves  of  the  grass  at  first 
and  later  defoliated  the  entire  field,  giving  it  the  appearance  of  suffer- 
ing from  drought,  although  the  month  of  July  was  moderately  wet. 
Many  farmers  wondered  why  their  rowen  was  apparently  burning 
idp,  but  they  did  not  investigate  until  the  worms  had  started  their 
'march  which  was  directed,  in  most  instances,  towards  the  corn  crop. 
After  once  becoming  established  in  corn,  it  is  very  difficult  to  find 
efficient  means  of  control.  Arsenate  of  lead  as  a spray  is  not  practical 
there,  as  the  lead  is  sure  to  collect  in  the  sheath  of  the  corn  in  sufficient 
amount  to  be  harmful  to  cattle  if  the  stalks  are  to  be  used  as  fodder. 
Experiments  with  hellebore  demonstrated  that,  that  insecticide  is  of 
.doubtful  value  after  the  larvae  have  become  half  grown  as  is  usually 
'the  case  when  they  attack  corn.  The  larvae  crawled  down  into  the 
sheaths  of  the  corn  during  the  day  (Fig.  1)  to  such  an  extent  that 
nearly  every  sheath  was  full.  Several  farmers  tried  hand  picking, 
but  the  following  day  they  found  the  sheaths  again  occupied,  although 
they  had  apparently  protected  the  field  thoroughly  by  furrows  and 
postholes.  Investigation  disclosed  that  after  the  sheaths  were  filled 
with  the  worms,  thousands  of  them  found  protection  during  the  day 
in  the  ground  at  the  base  of  the  stalks  from  which  position  they 
emerged  at  night  to  climb  up  and  devour  the  leaves.  If  there  was 
room  in  the  sheaths  when  day  approached  they  found  shelter  there, 
but  if  not,  they  again  found  protection  under  ground.  Over  one 
hundred  worms  were  frequently  unearthed  around  a single  hill  of 
corn. 

The  Assistant  Entomologist  made  many  visits  in  the  evenings  to 
the  infested  fields  to  study  the  habits  of  the  insects.  In  the  stillness 
of  the  night  the  gnawing  of  the  immense  number  of  insects  was 
plainly  audible. 

When  the  Army  Worm  invaded  oats  and  millet  its  work,  while 
fully  as  disastrous,  was  not  so  conspicuous  as  it  was  in  the  corn.  It 
fed  on  the  lower  leaves  first,  later  attacking  the  upper  leaves  and  then 


Digitized  by  the  Internet  Archive 
in  2017  with  funding  from 

.b  University  of  Illinois  Urbana-Champaign  Alternates 


cr 


https://archive.org/details/armywormOOrhod 


Fig.  1. — Larvae  of  the  Army  Worm  feeding  on  sweet  corn.  (Original.) 


5 


the  head.  In  a few  cases  the  head  was  eaten  first.  If  the  main  body 
of  the  larvae  did  not  wTork  on  the  outer  part  of  the  field,  the  whole 
crop  would  become  despoiled  before  their  work  was  noticed.  Where 
these  crops  were  attacked,  the  owners  were  advised  to  cut  them  at 
once  and  convert  them  into  hay  and  at  the  same  time  to  turn  a 
double  furrow  around  the  field  so  that  the  insects  could  not  invade 
other  crops.  In  most  cases  there  was  not  much  of  the  crop  to  save, 
but  the  making  of  the  furrows  resulted  in  the  destruction  of  hundred 
of  thousands  of  the  worms.  One  farmer  who  observed  the  worms 
at  work  in  the  early  stages  cut  his  oats,  but  was  unable  to  cure  the 
crop  because  of  wet  weather.  When  the  oats  were  ready  to  haul  in 
there  was  very  little  but  stems  left  as  the  larvae  fed  on  the  prostrate 
crop.  It  "would  probably  be  better  in  such  cases  to  shake  out  the 
oats  carefully  and  carry  them  to  some  other  field  to  make.  Indeed, 
this  was  done  with  millet  on  one  farm  in  Lonsdale  with  entire  success. 

In  grass  lands  of  considerable  extent,  the  Army  Worm  spread  out 
in  all  directions  and  reached  maturity  without  acquiring  the  marching 
habit.  Probably  more  harm  is  done  under  such  conditions  than 
when  marching.  Many  a beautiful  field  of  rowen  was  thus  cut 
down  to  the  stubble  left  by  the  mowing  machine.  In  such  fields,  the 
larvse  frequently  assumed  a vertical  position  on  the  shady  side  of  the 
stubble  in  the  daytime,  As  they  were  then  two-thirds  grown  and 
had  changed  from  a bla  ckish  color  to  one  with  alternate  dark  and  light 
stripes,  they  were  inconspicuous  and  one  might  pass  through  such 
field  from  end  to  end  in  bright  sunlight  without  seeing  them  unless 
he  were  a close  observer.  In  fact  the  writer  had  difficulty  in  making 
one  farmer,  who  had  appealed  for  help,  see  them  although  nearly 
every  stubble  had  two  of  the  larvse  present  in  an  upright  position. 
If  one  walked  across  the  field  with  the  sun  at  his  back  not  one  could 
be  seen.  If  one  walked  facing  the  sun  the  dark  and  light  lines  so 
blended  in  with  the  stubble  that  it  was  almost  impossible  to  see  the 
insects  from  an  upright  position.  If  one  stooped  over  and  looked 
across  the  field  in  a quartering  position  with  relation  to  the  sunlight, 
t he  enormous  number  of  the  larvse  became  at  once  apparent.  Burning 


6 


over  such  a field  will  result  in  the  destruction  of  most  of  the  insects 
as  also  will  rolling  it  with  a heavy  land  roller. 

DESCRIPTION  OF  THE  ARMY  WORM 

THE  MOTH 

The  moth  of  the  Army  Worm  is  shown  in  natural  size  in  Fig.  7. 
It  is  of  a dull  brownish  color  with  a white  spot  in  the  centre  of  each 
wing.  There  is  a row  of  dark  spots  along  the  lower  border  of  the 
wings  and  an  irregular  occurrence  of  dark  lines  running  across  the 
fore  wings  diagonally. 

THE  LARVA 

The  larvae  are  almost  smooth,  naked  caterpillars,  not  worms, 
(Fig.  5).  When  they  are  hatched  from  the  eggs  they  are  a light 
brown  color,  but  soon  change  to  a greenish  black.  As  they  molt  and 
grow,  they  acquire  distinct  longitudinal  stripes  and  lines  which 
extend  the  whole  length  of  the  body.  Some  of  the  stripes  are  greenish 
black,  some  are  of  a light  straw  color  and  some  of  the  lines  are  white. 
When  full  grown  the  larvae  are  about  one  and  one-half  inches  long. 

THE  PUPA 

The  pupa  is  of  a light  brown  color  when  it  is  first  made,  but  it 
gradually  acquires  a deep  brown  tinge.  One  is  shown  in  natural  size 
in  Fig  7.  The  eggs  are  small  globe-shaped  bodies  and  are  covered 
with  a white  secretion  which  becomes  the  first  food  of  the  newly 
hatched  larvae. 

LIFE  HISTORY 

The  Army  Worm  belongs  to  the  great  group  of  Owlet  Moths 
(. Noctuidce ) which  includes  the  cutworms.  It  is  generally  supposed 
that  the  insect  lives  over  the  winter  as  a partly  grown  caterpillar, 
completing  its  growth  in  the  early  spring,  pupating  in  April  and 
coming  forth  in  the  moth  stage  about  the  first  of  May.  Some  moths 
are  about  before  this  date  probably  emerging  from  over-wintering 


pupae. 


Fig.  5. — Larvae  of  the  Army  Worm,  natural  size.  (Original.) 

, young  larva;  b,  partly  grown  larva;  c,  full  grown  larva;  d,  larva  curled 


Fig.  7. — Moth  and  pupa  of  Army  Worm,  natural  size.  (Original.) 


7 


Some  writers  claim  that  they  winter  in  all  three  stages,  larval, 
pupal,  and  adult.  The  moths  lay  their  eggs  in  the  soil  around  grass 
roots  or  in  the  soil  of  weed  infested  borders  of  cultivated  fields.  The 
eggs  hatch  about  the  15th  of  May  in  Rhode  Island  and  become  full 
grown  in  about  a month.  The  larvae  pupate  about  the  middle  of 
June  and  the  adults  emerge  about  July  1st.  These  mate  almost  at 
once,  but  they  do  not  lay  their  eggs  for  four  or  five  days.  The  resulting 
brood  is  the  one  which  is  the  most  numerous  and  which  does  the 
greatest  amount  of  damage  in  Rhode  Island.  The  larva?  of  this  brood 
become  full  grown  and  go  into  the  pupal  stage  about  August  4th.  The 
adults  emerge  from  the  pupae  about  the  20th  of  August.  They  were 
numerous  around  the  street  lights  on  Exchange  Place,  in  Providence, 
on  the  21st,  22nd  and  23rd  of  August,  and  they  invaded  the  Federal 
Building  in  such  numbers  that  it  was  necessary  to  use  the  vacuum 
cleaner  to  get  rid  of  their  dead  bodies.  Some  entomologists  claim 
that  a number  of  the  pupae  of  the  second  brood  remain  under  ground 
in  that  stage  all  winter,  but  persistent  searching  by  the  writer  failed 
to  disclose  any  pupae  of  this  brood  after  the  main  flight  occurred  and 
furthermore  moths  emerged  from  everyone  of  several  hundred  pupae 
of  this  brood  which  were  reared  in  the  insectary.  It  is  generally 
supposed  that  the  moths  which  emerge  about  the  20th  of  August  lay 
eggs  which  produce  over-wintering  larvae.  This  would  complete 
the  life  cycle.  This  life  cycle  is  true  for  the  greater  number  of  the 
insects,  but  individuals  vary  from  it  to  such  an  extent  that  it  is 
possible  to  find  larvae  of  all  sizes,  pupae,  and  adults  during  any  of 
the  summer  months,  although  not  in  sufficient  numbers  to  make  it 
necessary  to  take  them  into  account  from  an  economic  standpoint. 

In  1914,  at  least,  there  was  some  important  variations  in  the 
life  cycle.  The  larvae  of  the  third  brood  proved  very  numerous  in 
some  sections  and  the  writer  found  them  of  all  sizes  on  October  29th, 
on  the  Hervey  Farm  at  Dugaway  Hill.  Some  were  feeding  on  oats, 
although  there  had  been  a severe  frost  on  the  two  nights  preceding. 
Many  were  curled  up  under  ground,  while  some  had  pupated.  As  a 
great  majority  of  the  larvae  were  not  over  half  grown  it  is  reasonable 


8 


to  suppose  that  they  will  live  over  the  winter  in  that  stage.  That 
some  of  them  reached  the  pupal  stage  is  probably  due  to  the  abnor- 
mally warm  weather  obtaining  during  October  which  permitted  them 
to  feed  much  later  than  is  usually  the  case. 

METHODS  OF  CONTROL 

As  with  other  cutworms;  the  Army  Worm  can  probably  best  be 
controlled  by  a proper  rotation  of  crops  and  by  clean  cultivation. 
In  the  majority  of  cases  the  infestations  have  their  origin  in  grass 
lands  which  have  not  been  turned  over  in  some  years,  or  in  weed- 
infested  borders  of  fields.  There  was  not  a single  instance  of  a first 
brodd  infestation  in  fields  which  had  received  late  fall  or  early  spring 
plowing.  If  the  worms  were  present  in  a neglected  field  during  the 
previous  year  burning  over  early  in  May  would  result  in  the  destruc- 
tion of  most  of  the  eggs  which  are  laid  previous  to  that  time  and  plow- 
ing and  harrowing  would  destroy  such  as  survive  the  burning  as  well 
as  the  over-wintering  larvae  and  pupae. 

During  the  first  two  weeks  in  July  careful  observations  should  be 
made  frequently  of  grass  lands  and  lands  which  have  been  planted 
with  millet  and  oats.  The  importance  of  this  cannot  be  over  em- 
phasized. If  the  Army  Worm  is  located  when  it  first  begins  to  work 
it  is  comparatively  easy  to  take  measures  for  keeping  it  within 
bounds.  In  making  observations  it  will  be  necessary  to  look  sharp, 
for  the  small,  black  larvae  may  be  easily  overlooked.  The  frass  about 
the  base  of  grass  stems  is  an  evidence  that  they  are  present  and  they 
may  be  disclosed,  also,  by  shaking  the  growing  grass  or  grain,  for 
at  the  slightest  disturbance  they  drop  to  the  ground  and  curl  up 
(Fig.  5d) . One  ought  to  dig  about  the  ground  at  the  base  of  the  stalks 
as  they  usually  hide  under  the  surface  during  the  day  and  they  may 
be  found  under  any  temporary  shelter  such  as  flat  stones,  pieces  of 
paper,  or  clumps  of  matted  grass.  If  it  is  found  that  they  are  present 
in  any  considerable  numbers,  a survey  should  be  made  to  determine 
the  extent  of  the  land  that  is  infested.  Immediately  after  this  is 
done,  the  crop  should  be  cut  and  a deep  furrow  plowed  around  the 


Fig.  2. — A well  made  furrow  and  one  which  will  act  as  a sufficient  trap  for  the 
Army  Worm.  The  stakes  indicate  the  post  holes  for  trapping  the  caterpillar. 

(Original.) 


Fig.  3. — A shallow  insufficient  furrow  (Original.) 


9 


land  infested,  with  the  steep  side  away  from  the  field  and  toward  the 
crops  to  be  protected.  This  furrow  should  be  carefully  made  and 
whenever  the  side  becomes  broken  down  it  should  be  straightened  by 
the  use  of  a spade.  The  loose  dirt  should  be  removed  from  the  furrow 
and  postholes  a foot  deep  should  be  dug  at  distances  of  about  a 
rod  apart  in  the  bottom  of  the  furrow  (Fig.  2).  A double  furrow  will 
be  found  to  be  more  efficient  than  a single  one.  The  crop  should  be 
cured  and  removed  from  the  field  as  soon  as  possible,  taking  care  to 
shake  out  the  larvae.  They  will  generally  fall  to  the  ground  at  the 
least  disturbance.  With  their  food  supply  removed,  the  worms  will 
attempt  to  leave  the  field  in  search  of  more  and  thus  get  into  the 
furrow.  They  cannot  climb  the  steep  side  of  the  furrow  readily 
and  will  crawl  along  it  seeking  some  easier  means  of  egress,  eventually 
falling  into  the  postholes.  Here  they  may  be  destroyed  easily  by 
spraying  them  with  kerosene  or  by  crushing  them  with  a tamper. 
Do  not  cover  them  with  soil  to  destroy  them  because  those  which  are 
full  grown  will  pupate  and  will  later  fly  to  lay  more  eggs  for  a future 
brood. 

This  same  method  will  also  serve  as  an  efficient  means  of  control 
whenever  the  worms  have  started  to  march  for  any  cause.  In  fact, 
furrows  should  be  plowed  with  the  steep  side  toward  the  crops  to  be 
protected  whenever  Army  Worms  are  present  anywhere  in  the  neigh- 
borhood for  they  travel  rapidly  night  and  day  until  they  find  just 
the  food  which  they  desire.  Too  much  stress  cannot  be  given  the 
matter  of  making  a sufficient  furrow.  Shallow’,  broken  down  furrows 
are  valueless  and  yet  the  writer  found  many  instances  of  such  futile 
attempts  to  check  the  advance  of  the  Army  Worm  in  his  visits  to 
infested  farms  in  1914.  See  (Fig.  3). 

Whenever  Army  Worms  are  found  on  lawns  or  on  grass  which  is 
not  to  be  used  as  food  for  animals  they  can  be  destroyed  easily  by 
applying  a spray,  consisting  of  one  pound  of  arsenate  of  lead  to  twelve 
gallons  of  water.  If  for  any  reason  it  is  undesirable  to  use  poison 
good  results  may  be  obtained  by  going  over  the  ground  with  a land 
roller,  especially  if  this  is  done  in  the  evening. 


10 


The  Army  Worm  seldom  if  ever  gets  its  first  start  in  corn,  but  if 
through  neglect  of  taking  the  above  mentioned  precautions,  it  does 
get  established  there,  it  will  generally  be  found,  at  first,  that  only  part 
of  the  crop  is  infested.  The  farmer  should  at  once  examine  the  crop 
by  looking  into  the  sheaths,  and  by  loosening  up  the  soil  around  the 
roots,  in  order  to  determine  how  far  the  worm  has  advanced  into  the 
field.  Almost  always  they  work  in  from  the  side  or  end  of  the  field 
first.  (Fig.  4).  Furrows  as  described  above  should  be  made  at 
once  separating  that  part  of  the  field  which  is  infested  from  that  which 
is  not.  This  will  generally  result  in  the  saving  of  a greater  part  of  the 
corn.  If  for  any  reason  it  is  not  desirable  to  make  a furrow  it  would  be 
well  to  sacrifice  a half  dozen  rows  of  corn  next  to  the  infested  rows  and 
spray  same  with  arsenate  of  lead.  These  rows  should  be  carefully 
marked  so  that  the  stalks  do  not  reach  the  stock  as  fodder.  It  will 
be  necessary  to  do  the  spraying  thoroughly  and  persistently  as  the 
nature  of  the  corn  leaves  is  such  that  the  spray  will  not  stick  to  them 
as  readily  as  it  does  to  the  leaves  of  trees. 

If  the  greater  part  of  the  corn  has  become  infested,  the  larvae  can 
be  handpicked  from  the  sheaths  and  from  under  the  soil  around  the 
base  of  the  stalks.  This  is  a rather  slow  and  expensive  method,  but 
it  can  be  made  effective.  An  alternative  measure  would  be  to  go 
through  the  corn  in  the  daytime  hitting  each  stalk  a hard  rap.  This 
will  dislodge  many  of  the  larvae  which  will  find  shelter  under  the 
surface  of  the  ground  until  nightfall.  Immediately  after  a small 
amount  of  poison  bran  mash  may  be  scattered  around  the  hills.  It 
has  been  found  by  experiment  that  the  larvae  when  coming  out  at 
night  will  eat  the  nearest  food,  which  in  this  case  would  be  the  poi- 
soned bran,  rather  than  to  laboriously  climb  up  the  stalks  to  the 
leaves.  This  mash  is  made  by  mixing  one  pound  of  Paris  green  with 
50  pounds  of  bran,  stirring  it  up  with  diluted  molasses  and  the  juice 
of  one-half  dozen  lemons  or  oranges  until  it  has  the  consistency  of  stiff 
dough.  In  many  western  states  where  thousands  of  acres  of  corn 
sometimes  becomes  infested  with  the  Army  Worm  the  poisoned 
bran  is  scattered  broadcast  over  the  fields  and  a handful  is  thrown  into 


Fig.  4. — Field  of  sweet  corn,  attacked  on  outside  edge  by  the  Army  Worm.  (Original.) 


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the  curl  of  the  corn.  This  method  has  been  found  almost  one 
hundred  per  cent,  efficient  and  can  be  employed  at  a cost  of  about 
twenty-five  cents  per  acre.  The  poison  bait  is  more  effective  when 
scattered  in  the  early  evening. 

One  farmer  turned  his  hens  and  chickens  into  a small  field  of  oats 
wdfich  was  badly  infested  with  the  result  that  nearly  every  worm  was 
devoured.  In  the  West  hogs  are  sometimes  let  loose  to  good  purpose 
when  the  worms  are  numerous. 

The  Army  Worm  moth  is  attracted  to  bright  lights  to  a greater 
extent  than  is  that  of  almost  any  other  species.  At  times  of  their 
flight,  millions  may  be  destroyed  before  their  eggs  are  laid,  by  sus- 
pending lanterns  above  receptacles  containing  water  covered  with  a 
thin  layer  of  kerosene  and  placed  in  infested  fields. 

CROPS  ATTACKED  BY  ARMY  WORM 

The  Army  Worm  confines  its  depredations  as  a rule  to  plants 
uf  the  grass  family  such  as  millet,  oats,  timothy,  barley,  herd ’s  grass, 
wild  grasses,  and  corn.  It  does  not  feed  on  the  common  garden 
vegetables,  as  many  feared  it  would,  when  it  infested  their  grass  lands. 
Some  truck  gardeners  went  to  considerable  trouble  to  keep  them  out 
of  crops  of  tomatoes,  which  they  would  not  harm  in  any  way.  It 
seldom  eats  clover  or,  for  that  matter,  anything  else  except  such 
as  those  which  have  been  enumerated  so  that  the  farmer  need  not 
take  into  account  the  ordinary  vegetable  crops  when  planning  to 
circumvent  the  Army  Worm. 

CAUSE  OF  INFESTATION  OF  1914 

Some  of  the  most  frequent  questions  asked  during  the  summer  of 
1914  were  “ Where  does  the  Army  Worm  come  from?”  “Why  is 
it  so  numerous  this  year?  ” “ Will  it  be  here  in  just  as  great  numbers 

in  1915?”  Perhaps  no  definite  answers  can  be  made  to  any  of  these 
questions.  There  are  two  factors  which  have  some  bearing  on  the 
relative  number  of  Army  Worms  present  in  any  particular  year. 


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Probably  the  principal  factor  is  the  matter  of  parasites.  If  the 
parasites  have  been  on  the  increase  through  a series  of  years  so  that 
their  attack  has  reduced  the  number  of  Army  Worms  to  a minimum, 
the  parasites  eventually  will  starve  out  and  become  almost  extermi- 
nated. This  condition  gives  such  of  the  Army  Worms  as  remain  the 
opportunity  to  multiply.  As  the  moth  lays  five  or  six  hundred  eggs 
it  would  not  take  very  long  for  them  to  increase  to  immense  numbers 
if  there  was  no  check  of  any  kind  placed  upon  them.  The  same  thing 
would  obtain  if  the  parasites  became  destroyed  through  unfavorable 
weather  conditions  or  by  the  abundance  of  secondary  parasites.  It 
is  possible  that  the  parasites  of  the  Army  Worm  were  scarce  during 
the  season  of  1913-14  and  thus  the  insect  was  enabled  to  increase 
to  such  tremendous  numbers. 

Some  entomologists  believe  that  during  a time  of  favorable  winds 
enormous  numbers  of  the  moths  are  swept  northward  from  states  to  the 
South.  Experiments  are  now  being  carried  on  to  determine  whether 
or  not  this  is  so.  It  is  highly  probable  that  this  is  so  for  frequently, 
as  happened  on  October  19th,  20th  and  21st  during  the  fall  of  1914,  an 
immense  flight  of  a near  relative  of  the  Army  Worm,  the  Cotton 
Moth,  invaded  Rhode  Island.  They  were  nearly  as  thick  around  the 
lights  on  Exchange  Place  as  were  the  Army  Worm  Moths  during  the 
latter  part  of  August  and  almost  everybody  mistook  them  for  the 
moths  of  the  Army  Worm.  As  the  Cotton  Moth  larvae  feed  only  on 
the  cotton  plant  it  will  be  seen  that  the  moths  must  have  traveled 
great  distances  to  reach  Rhode  Island. 

A study  of  the  weather  maps  for  October  16th,  17th,  18th  and  19th, 
1914,  discloses  the  fact  that  a low  pressure  area  passed  up  the  Missis- 
sippi Valley  and  swung  across  New  England.  As  the  tendency  of 
the  air  around  a low  pressure  area  is  to  move  towards  its  centre  the 
Cotton  Moth  probably  had  its  journej^  directed  and  accelerated  by 
this  inflowing  air.  As  there  are  five  or  six  broods  of  Army  Worms 
reared  in  the  South  every  summer  it  is  highly  probable  that  it  may 
frequently  reach  us  in  a similar  manner  and  this  may  account  in 
part  for  the  infestation  which  visited  us  this  year. 


Fig.  6. — Larva  of  Army  Worm  X5  with  three  eggs  of  a parasitic  tachina  fly 
attached  to  back.  (Original.) 


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It  would  be  impossible  to  predict  as  to  the  number  of  Army  Worms 
which  we  may  anticipate  another  year.  It  is  seldom  that  they  are 
numerous  for  two  years  in  succession.  A large  number  of  them  were 
parasitized  during  the  latter  part  of  the  season  and  it  is  probable  that 
the  increase  of  these  parasites  will  tend  to  hold  them  in  check. 
Probably  weather  conditions  will  have  much  bearing  on  the  number  of 
these  insects  which  may  be  present  another  year. 

ENEMIES  OF  ARMY  WORMS 

Many  birds  are  consistent  feeders  on  the  Army  Worm.  Large 
flocks  of  grackles  were  observed  eating  Army  Worms  in  several 
sections.  Red-wing  blackbirds,  robins,  meadow-larks,  cow  birds, 
song  sparrows,  field  sparrows,  chipping  sparrows,  brown  threshers, 
bob-whites,  starlings,  and  even  the  much  detested  English  sparrows 
devoured  an  immense  number  of  the  worms.  One  bob-white  became 
so  repleted  with  the  insects  that  he  was  scarcely  able  to  fly.  One 
misguided  farmer  granted  permission  to  some  Italians  to  shoot  the 
blackbirds  which  had  gathered  in  immense  numbers  on  his  estate  to 
feed  on  the  worms  which  were  destroying  his  corn.  Whatever  may 
be  said  in  disparagement  of  the  blackbird  it  is  certain  that  no  other 
bird  does  such  yeoman  service  as  he  in  ridding  fields  of  this  disastrous 
pest. 

There  are  some  predaceous  insects  which  feed  on  the  Army  Worm, 
notably  the  Digger  wasp  and  both  the  larvae  and  adult  of  some 
Calosoma  beetles. 

The  most  important  enemy  of  the  Army  Worm  is  a parasitic 
tachina  fly.  This  fly  sticks  her  eggs  on  the  back  of  the  Army 
Worm  near  the  neck  (See  Fig.  6)  and  the  young  maggot  hatches  and 
burrows  into  the  host  where  its  depredations  encompasses  the  death 
of  the  worm.  As  this  fly  completes  its  life  cycle  in  a few  days,  it 
increases  so  rapidly  in  numbers  that  in  favorable  seasons  it  is  difficult 
to  find  a single  worm  of  the  third  brood  that  has  not  been  parasitized. 
During  the  week  between  July  15th  and  22d,  there  were  very  few 
worms  parasitized,  but  nearly  all  the  worms  seen  after  August  1st 


14 


had  one  or  more  eggs  of  this  fly  attached  to  their  backs.  The  flies 
hovered  over  the  postholes,  dug  in  the  furrows  to  trap  the  Army  Worm, 
in  large  numbers  and  the  result  of  their  work  ought  to  be  apparent  in 
1915. 

The  Army  Worm  is  sometimes  attacked  by  a fungus  belonging  to 
the  genus  Empusa  which  decimates  their  ranks  to  a great  extent, 
especially  in  wet  seasons.  It  is  also  subject  to  a bacterial  disease 
commonly  called  the  wilt  disease  since  the  caterpillar  infected 
appears  to  be  wilted.  When  this  disease  obtains  a foothold  it  fre- 
quently wipes  out  whole  armies  of  the  worm.  There  seemed  to  be 
little  of  this  disease  present  in  1914,  and  this  may  partially  account 
for  the  severity  of  the  infestation. 


& 


